On the go and no time to finish that story right now? Your News is the place for you to save content to read later from any device. Register with us and content you save will appear here so you can access them to read later.

Electric vehicles are far more useful to New Zealand for reducing carbon emissions than rooftop solar power, says a new study by energy industry consultants Concept.

The Wellington-based consultancy contains some of the electricity industry's most experienced analysts, who have published their findings in the first of three reports backed by Consumer New Zealand, the Energy Efficiency and Conservation Authority, three major electricity retailers, and three electricity network owners.

It concludes that photovoltaic electricity generation, mainly through rooftop solar installations that can be linked to battery storage, will have less impact on carbon emissions in the long term than EVs because solar will start substituting other renewable electricity generation options, such as wind, geothermal or hydro.

EVs, on the other hand, will largely eliminate carbon emissions from petrol and diesel because so much of New Zealand's electricity is generated from renewable sources.

"This analysis shows that in the New Zealand context, EVs offer much greater emissions benefits than solar PV or batteries, with the widespread uptake of solar PV over the long-term expected to moderately increase emissions," says Concept.

That's because solar power would be disproportionately generated during the summer months, when sunshine hours are longest, while New Zealand's electricity needs are greatest in winter. Solar PV would displace renewable alternatives that would be more available in the winter months, causing greater reliance on fossil fuel-fired electricity generation to meet total demand. In the New Zealand context, that would mainly be natural gas-powered 'peaker' stations, capable of being turned off and on quickly in response to spikes in demand.

... in the New Zealand context, EVs offer much greater emissions benefits than solar PV or batteries, with the widespread uptake of solar PV over the long-term expected to moderately increase emissions.

The Concept study is highly specific to New Zealand for two reasons. Firstly, in most countries, EVs would be drawing more electricity from fossil fuel-sourced electricity generation than renewable, where renewables are a small part of the electricity mix, whereas they already provide about 80 percent of New Zealand's electricity mix.

WATCH: Air NZ moves to all-electric vehicle fleet:

Air NZ has announced it's moving towards a fully electric car fleet. See a video supplied by the airline explaining the move.

Secondly, unlike hot countries such as Australia, New Zealand's peak energy demand is in winter for heating rather than for air-conditioning during summer, when solar generation is also most available.

"Increasing the seasonal gap between winter power demand and supply would likely increase the need for fossil-fuel power stations that operate on a seasonal basis, noting that New Zealand's hydro stations are limited in their ability to increase the amount of water they store in summer to release in winter," the report finds.

EVs directly displace emissions from fossil-fueled vehicles and in New Zealand, the power to charge EVs will come mainly from renewable power stations. This means EVs provide significant net savings.

While surprising at first glance, the results made sense, said Concept director Simon Coates.

"Most of New Zealand's electricity is generated from renewable sources, Adding solar panels basically means that New Zealand will need to build fewer renewable power stations - with little or no net carbon saving," he said. "On the other hand, EVs directly displace emissions from fossil-fueled vehicles and in New Zealand, the power to charge EVs will come mainly from renewable power stations. This means EVs provide significant net savings."

The Green Party and environmental lobbyists have been pressing for greater support to both solar PV and EVs. While the government has shown no appetite for encouraging solar PV, Energy Minister Simon Bridges has been talking for more than a year about an EV policy without delivering.

Concept estimates an electric car (EV) could reduce annual carbon emissions by around 1.4 tonnes per year in the short to medium term and up to 1.7 tonnes annually in the long term.

By contrast, a 4 kilowatt solar panel is estimated to save 0.35 tonnes of carbon in the short to medium term, but to increase emissions by 0.26 tonnes in the long term. A home battery is estimated to save 0.08 tonnes and 0.05 tonnes respectively in the short/medium and long terms respectively. Solar PV and battery technology could set a household back by $10,000 to $12,000 to install, the report said.

WATCH: Norway's electric vehicle revolution:

NZ Herald writer Grant Bradley investigates how Norway has moved to have the world's fastest growing electric vehicle fleet.

Media reports last week revealed that Nissan stopped offering the only affordable EV family saloon, its Leaf model, for sale in New Zealand last November. EVs cost more up-front than petrol or diesel cars, despite costing far less to run over their lifetimes.

Comparing Australia and New Zealand, the report shows what large differences there can be between countries' most carbon-cutting energy choices.

"Compared with New Zealand, the emissions benefits of Australian EVs are not as great because much of the power for charging them comes from coal or gas-fired power stations," Coates said. "Conversely, Australian solar PV offers much greater emissions savings than in New Zealand because Australian solar largely displaces fossil-fuelled power stations."